TBC1D15 affects glucose uptake by regulating GLUT4 translocation.

Glucose transport into skeletal muscle is mediated by the principal glucose transporter protein, GLUT4, which can be transported from intracellular vesicles to the cytoplasmic membrane, and the translocation of GLUT4 vesicles requires a variety of Rab proteins. Previously we reported a new type of TBC1D15 from C. plagiosum with Rab-GAP activity for Rab7. Here we reported that TBC1D15 regulated glucose uptake by affecting the translocation of GLUT4 through late endosomal pathway. When TBC1D15 was knocked out by CRISPR/Cas9, a significant reduction in 2-NBDG uptake was observed, and the total amount of GLUT4 was significantly reduced in TBC1D15-/- cells compared to that in WT cells. Furthermore, concentrated distribution of Rab7 in Lamp1-decorated late endosome/lysosome and an increase in co-localization between GLUT4 and Rab7 was observed in TBC1D15-/- cells. These results suggested that TBC1D15 served as a master regulator in GLUT4 translocation and further affected GLUT4-mediated glucose uptake.